They save.

Use the power of compound interest.
Business Insider/Andy Kiersz

A Bankrate survey of 1,003 people found that 69% of those ages 18-29 had no retirement savings at all. Twenty-somethings who don't have enough foresight to recognize that one day they're going to retire and need money to live on are missing out on years of money gained through interest.

Entrepreneur Aditya Rathnam writes on Quora there's no need to start investing too much, since you're just starting your career, but it's essential to take advantage of your company's 401(k) matching program, if one is available, and/or open an IRA account.

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They develop a debt-repayment plan.

Figure out a way to eliminate debt as soon as possible.
Robert Mecea/AP Images

Seventy percent of college students graduated with an average of $30,000 in student-loan debt last year, but that doesn't mean that debt is somehow a badge of adulthood.

They take care of their health.

Taking care of your body is worth the effort.
Thomson Reuters

As each year goes by, it becomes harder to start a sustained exercise regimen, and harder still to recover from a late night of drinking.

While you're still young, says Quora user Mo Seetubtim, develop healthy habits that will set you up for the next phase of life. Enjoy your vices in moderation, eat well, and choose a workout over a happy hour now and then.

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They're persistent.

The most successful people don't always win, but they do always pick themselves up.
MGM/Netflix

If you're an ambitious 20-something who thinks that adulthood means having things figured out, then getting fired from a job, ending a serious relationship, or having your company fail can be devastating. But the truly successful are able to learn from what went wrong and move forward all the wiser.

"Getting fired and waking up the next day as usual made me realize that failure isn't the end of the world. Getting dumped taught me the difference between a good and a bad relationship, something I already knew inside but refused to accept until the bad relationship was over," says Carolyn Cho on Quora.

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They don't try to please everyone.

You don't need to be everyone's friend.
Instagram/antikvarus

Your 20s are a time to start building a network that will establish a foundation for your career. If you know that, it's a good idea to be on friendly terms with your boss, clients, and all of your coworkers.

Eventually, however, you're going to meet people you don't like and those who don't like you. That's normal, and not a sign that you should change yourself, as long as everything else is going well.

"Inevitably, someone will always dislike you. I wish I had figured this out a lot earlier and stopped trying so hard and worrying so much about it," says Cho.

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They're flexible.

Trying to follow a highly specific life plan is setting yourself up for heartache.
David McNew/Getty Images

While it's good to set career goals that keep you focused and motivated, you should avoid getting caught up in intricate five-year plans, Joe Choi says on Quora.

Author and investor James Altucher says that one of the main problems he's found among people in their 20s is that they get caught up in absolutes. He recommends keeping yourself flexible and open to new experiences. There's a good chance that the ideal life you envisioned for yourself at age 20 doesn't resemble the one that ultimately makes you happy at age 30.

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They take measured risks.

"With no family to feed and no dependents counting on you, your 20s are without a doubt the years to take a leap and pursue your passion," says Jessie Goldenberg, who abandoned a promising media career shortly after college to start her own business, the successful mobile fashion boutique Nomad.

Of course, taking risks to the point of being reckless is as bad or worse a habit than suppressing ambition. Investor and "The 4-Hour Workweek" author Tim Ferriss recommends taking the time to think through how to recover should your attempt fail and then seeing if it's worth the risk.

They don't isolate themselves.

When you're just starting out, you probably don't have much disposable income. But just because you can't take a weeklong ski trip in Switzerland doesn't mean you should confine yourself to the space between work and home.

Your 20s, Shikhar Argawal says on Quora, are a time when "you are mature enough to go out on your own and immature enough to learn from others." Break out of your bubble as much as you can afford to, and don't ignore career opportunities far from home if they arise.

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They maintain important relationships.

"Your college pals that you think will be your best pals for life? Some will still be there at 40, most will be living their lives doing their thing," writes Sutherland Cutter on Quora. As everyone is figuring out their lives, you'll realize that relationships take work to maintain.

It's worth staying in touch with former coworkers and buddies, though. The 1973 study "The Strength of Weak Ties" by Mark Granovetter of Johns Hopkins University found that the weak ties you share with acquaintances are most often the connections that get you ahead, since they have access to different networks and ideas from you.

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They associate with people who push them to be better.

LinkedIn founder Reid Hoffman, left, has dedicated his career to surrounding himself with impressive people.
Mike Blake/Reuters

Tech entrepreneur and author Ben Casnocha has worked closely with LinkedIn founder and chairman Reid Hoffman for several years and writes that the greatest lesson Hoffman taught him was "that you are the average of the five people you spend the most time around. You really are the company you keep."

There's no need for maintaining toxic personal or professional relationships out of loyalty.

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They let things go.

Meditation is an excellent technique for learning to keep your mind focused on the present.neonow/Flickr

Picking fights and holding grudges will make you miserable, Tatum says, whether that's in your personal or professional life.

You'll realize soon enough that your hard work won't always be recognized, either, Rahul Bhatt writes on Quora. But never let that be an excuse to be lazy or bitter.

They understand that their parents aren't always right.

Quora user Arpan Roy writes that as he looks back on his 20s, he's come to see that even though he loves his parents and appreciates their advice, it wasn't always the best for him.

As you grow older, you'll come to see your parents less as authority figures and more as people just doing the best they can. "After all, your parents are human, and humans are not correct all the time," Roy says.

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They're honest.

The deceitful manipulation of others and sucking up to superiors can only take you so far — they're not the keys to a lasting, fruitful career.

"The truth has a way of rearing its ugly head, so the sooner you can come to integrity with yourself and the world at large, the sooner you'll be able to get working towards what you really want, who you really want to be," Arjuna Perkins writes on Quora.

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They keep work from overtaking their personal lives.

Striking a balance between a fulfilled professional and personal life requires effort.
REUTERS/Carlo Allegri

"If I could go back in time, I'd introduce my 22-year-old self to a quotation by the writer Brian Andreas: 'Everything changed the day she figured out there was exactly enough time for the important things in her life,'" Huffington Post cofounder Arianna Huffington writes on LinkedIn.

And if you are obsessed with your work — whether or not you love it — understand that you will actually be making yourself more productive by allowing yourself to enjoy life.